The objective of this research is to investigate whether changes in poly(A) polymerase observed in response to various physiological stimuli and in tumorigenesis are due to alterations in the number of enzyme molecules or to modifications of the enzyme activity (e.g. phosphorylation). The number of enzyme molecules will be determined using the radioimmunoassay for poly(A) polymerase which was recently developed in our laboratory. This technique can detect nanogram quantities of the enzyme in tissue extracts. The antigenic relationship of the hepatoma poly(A) polymerase (against which the antibodies were produced) to the corresponding enzyme from liver and to the enzyme from the different cellular compartments, will be investigated. Preliminary studies have indicated that poly(A) polymerase can be phosphorylated by purified exogenous kinase in vitro. The phosphorylated enzyme is at least 3-fold as active as the control enzyme. The mechanism of activation will now be explored in detail. This will include studies on the primer specificities, binding of the enzyme to primer and the product size. The possible modification of the enzyme via phosphorylation in response to physiological stimuli will also be investigated. Finally the role of phosphorylation of poly(A) polymerase in facilitating the mRNA transport into the cytoplasm will be examined.